Question 1

Which are evolutionarily more closely related?

Accepted Answer

Archaea and eukarya are more closely related to each other than either is to bacteria. This is supported by molecular and cellular evidence, such as the similarity of their ribosomal RNA and the presence of membrane-bound organelles in eukaryotic cells that are absent in bacteria and archaea.

Question 2

An organic solvent widely used in industrial processes-1,1,1-trichloroethane (TCA)-is a major environmental pollutant affecting human health and damaging the ozone layer.Recently,researchers isolated the first bacteria able to degrade TCA.They found that the bacteria use hydrogen as an electron donor,TCA as electron acceptor,and acetate as a carbon source.Based on the preceding information,deduce the method used to isolate these bacteria.

Accepted Answer

Based on the information given, the method used to isolate these bacteria is likely an enrichment culture. Enrichment cultures involve selecting for microbial growth in a specific environment or medium, such as one containing TCA. By repeatedly transferring cultures to fresh media with TCA as the sole source of carbon and energy, the researchers were likely able to select for and isolate the bacteria that can degrade TCA.

Question 3

Which of the following describe all existing bacteria?

Accepted Answer

While some bacteria can be pathogenic, not all are harmful. Additionally, while there are some bacteria that live in extreme environments, this is not a characteristic shared by all bacteria. However, all bacteria are tiny, exist in almost all habitats, and have a wide variety of metabolic capabilities, making option D the best description of existing bacteria.

Question 4

Bacteria and Archaea are most easily distinguished from each other by their

Accepted Answer

The answer of Bacteria and Archaea are most easily distinguished...

Question 5

You need to identify the major type of bacteria living on the shower curtain in your bathroom and find out what they use as a food source.What is the most efficient method for answering this question?

Accepted Answer

Enrichment culture would be the most efficient method in this case because it allows for the selective growth of specific types of bacteria based on their preferred nutrients. By exposing the bacteria from the shower curtain to different nutrient sources in the enrichment culture, researchers can identify which ones the bacteria prefer and therefore determine what their food source is. Direct sequencing could be used to identify the bacteria present on the curtain, but it would not necessarily reveal their food source.

Question 6

You might be interested to know how many different types of bacteria live on the shower curtain in your bathroom.What is the most efficient method for answering this question?

Accepted Answer

Direct sequencing is the most efficient method for identifying the different types of bacteria on the shower curtain. Enrichment culture involves selectively providing specific nutrients for growth of certain bacterial types, but may miss other types that require different nutrients. Direct sequencing, in contrast, allows for a broad survey of all bacterial types present based on DNA analysis.

Question 7

Starting in 1945,Escherichia coli became a bacterium of choice to study basic cellular processes and gene function.What specific feature of E.coli is responsible for its rise to prominence as a model system?

Accepted Answer

The answer of Starting in 1945,Escherichia coli became a bacterium...

Question 8

What do Bacteria have in common with Archaea but not with Eukarya?

Accepted Answer

The answer of What do Bacteria have in common with...

Question 9

Use of synthetic fertilizers often leads to the contamination of groundwater with nitrates.Nitrate pollution is also a suspected cause of anoxic "dead zones" in the ocean.Which of the following might help reduce nitrate pollution?

Accepted Answer

Growing improved crop plants that have nitrogen-fixing enzymes can reduce the need for synthetic fertilizers, thereby reducing nitrate pollution.

Question 10

Multicellularity and large body size of eukaryotic organisms requires high metabolic rates and efficient ATP production by aerobic respiration.How did bacteria change Earth's atmosphere to enable aerobic respiration?

Accepted Answer

Oxygenic photosynthesis by cyanobacteria significantly increased the amount of oxygen in the atmosphere. Oxygen is a byproduct of photosynthesis and the cyanobacteria were the first organisms to perform oxygenic photosynthesis. As the amount of oxygen in the atmosphere increased, it allowed for the evolution of eukaryotic organisms with larger body sizes and higher metabolic rates that are dependent on aerobic respiration.

Question 11

What organisms are most numerous on Earth?

Accepted Answer

Prokaryotes, including bacteria and archaea, are the most abundant and widespread organisms on Earth. They are found in almost every environment, from soil to water to inside other organisms. While eukaryotes such as plants and insects are also numerous, they are far fewer in number compared to the vast amounts of prokaryotes.

Question 12

Microbiologists use the Gram stain to aid in identification of bacteria.What is the major difference between Gram-positive and Gram-negative bacteria?

Accepted Answer

Gram-positive bacteria have a thick peptidoglycan layer and no outer membrane, while Gram-negative bacteria have a thin peptidoglycan layer and an outer membrane.

Question 13

While examining a rock surface,you have discovered an interesting new organism.Which of the following criteria will allow you to classify the organism as belonging to Bacteria,but not Archaea or Eukarya?

Accepted Answer

The presence of cell walls made primarily of peptidoglycan is a characteristic trait of bacteria but not present in Archaea or Eukarya. Option A - unicellularity is not a unique feature of bacteria as many organisms in Archaea and Eukarya domains are also unicellular. Option C - absence of a nucleus can be seen in both Bacteria and Archaea. Option D - some species of Archaea are known to survive at temperatures over 100°C, so it is not a unique feature of bacteria.

Question 14

What is the goal of bioremediation?

Accepted Answer

The goal of bioremediation is to clean up areas polluted with toxic compounds by using living organisms, particularly bacteria. The process involves stimulating the growth of naturally occurring microorganisms, or introducing specific strains of bacteria, that can break down or absorb pollutants, thereby reducing their harmful effects on the environment.

Question 15

You have decided to grow E.coli to isolate a specific enzyme.For your experiment,which of the following conditions would enable you to grow a maximum amount of bacteria in the shortest time possible?

Accepted Answer

E.coli grows optimally at 37°C, which is its natural habitat temperature (human body temperature). Growing in suspension culture allows for better nutrient access and aeration, leading to faster growth compared to agar plates.

Question 16

Biologists sometimes divide living organisms into two groups: autotrophs and heterotrophs.How do these two groups differ?

Accepted Answer

Autotrophs are organisms that can produce their own organic molecules (such as glucose) from inorganic sources of carbon (such as carbon dioxide). In contrast, heterotrophs obtain their organic molecules by consuming other organisms or organic substances derived from other organisms. Therefore, autotrophs and heterotrophs differ in the sources of carbon they use for their metabolism.

Question 17

What is the right progression of steps for a direct-sequencing experiment?

Accepted Answer

In a direct-sequencing experiment, the typical progression is to first lyse cells to release the DNA, then purify the DNA, amplify the genes of interest using PCR, and finally, if needed, insert the amplified genes into plasmids for further analysis or manipulation.

Question 18

Imagine that you are given some chemoorganotrophic bacteria to grow.What should you use as a source of energy for this type of bacteria?

Accepted Answer

Chemoorganotrophic bacteria are organisms that obtain their energy from organic compounds. Sugar is a common source of organic compounds that can be readily metabolized by chemoorganotrophic bacteria for energy and growth. Light is a source of energy for photoautotrophic bacteria, methane is a source of energy for methanotrophic bacteria, and ammonia is a source of nitrogen for some bacteria, but none of these are suitable as a primary source of energy for chemoorganotrophic bacteria. Therefore, the best choice for a source of energy for chemoorganotrophic bacteria is D) Sugar.

Question 19

Researchers have found a new type of bacteria,and they want to determine its phylum.What would be the most reliable method to do so?

Accepted Answer

Determining the ribosomal RNA sequence of a bacterium is the most reliable way to determine its phylum as it provides information about its evolutionary relationships with other bacteria. Gram-stain tests and analysis of morphological characteristics are not always reliable indicators of phylum, as bacteria within the same phylum can have different cell wall structures and morphologies. Performing an analysis of metabolic pathways can provide insight into the bacterium's functional characteristics, but may not be as accurate in determining phylum as analyzing its RNA sequence.

Question 20

To establish a link between a specific bacterium and a skin disease,researchers have shown that bacterium was present in sick persons but not in healthy individuals.They isolated the bacterium in a pure culture and demonstrated that experimental healthy animals injected with this culture became sick.What other experiment do researchers need to perform to be absolutely sure that the bacterium is responsible for the disease?

Accepted Answer

The answer of To establish a link between a specific...

Quiz 28: Bacteria and Archaea